The present invention relates to the medical diagnostic arts. It finds particular application in conjunction with fourth generation CT scanners and will be described with particular reference thereto.
In fourth generation scanners, a continuous ring of x-ray detectors are mounted peripherally around the examination region. In order to accommodate the x-ray tube and other associated structure which conventionally rotates inside the ring, the detector ring is about one and a half meters in diameter.
Heretofore, a plurality of radiation detectors were mounted on each of a plurality of circuit boards. The circuit boards were constructed of conventional reinforced resin material a couple of millimeters thick which also supported various associated circuitry and electrical components. The circuit boards were flexible and could easily distort from the intended circular plane. Any deviation of the detectors from the prescribed circle could cause errors in radiation focus, image reconstruction, and otherwise degrade the resultant image.
In order to insure that the detectors conformed precisely to the prescribed circle, the circuit boards were securely mounted to a rigid, precision frame. For manufacturing convenience, the frame included twelve precast arcuate, tubular segments. The segments were precision machined such that they interconnected into a precise circle that would not flex or distort. This structure was mounted in the CT scanner cabinetry around the periphery of the detector circle and the circuit boards were mounted on the inner face thereof. Thus, the radiation struck the detectors before the cast supporting frame to avoid any interference with data collection.
Although the structures successfully held the detectors precisely in a prescribed circle, there were drawbacks. First, the precision machining of the inside surface, interconnecting edges, and the like to insure a precisely circular mounting surface for the detector boards was relatively expensive. Moreover, the pieces were cast relatively thick to assure rigidity and prevent flexing of the circuit boards. The segments proved relatively bulky and heavy in the crowded interior of a CT scanner.
In accordance with the present invention, a new and improved detector mounting arrangement is provided.